Capped and/or beveled jet blast resistant vehicle arresting units, bed and methods

ABSTRACT

Aircraft arresting beds at ends of runways may be subject to damaging effects of jet blast phenomena. Arresting units for that and other applications and which are resistant to such effects are described, with related methods.

BACKGROUND OF THE INVENTION

This invention relates to arresting the forward motion of vehicles, suchas (but not limited to) aircraft overrunning a runway, and moreparticularly to arresting embodiments with improved resistance to jetblast, moisture damage and other potentially destructive forces.

The problem of aircraft overrunning the ends of runways, with thepossibility of passenger injury and aircraft damage, is discussed inU.S. Pat. No. 5,885,025, “VEHICLE ARRESTING BED SYSTEMS” (which may bereferred to as “the '025 patent”). That patent, together with U.S. Pat.No. 5,902,068, “VEHICLE ARRESTING UNIT FABRICATION METHOD” (the '068patent) and U.S. Pat. No. 5,789,681, “ARRESTING MATERIAL TEST APPARATUSAND METHODS” (the '681 patent) describe arresting beds, units andfabrication methods and testing based on application of, for example,cellular concrete for arresting purposes. Improved arresting blocks,beds and methods are described in U.S. Pat. No. 6,685,387, “JET BLASTRESISTANT VEHICLE ARRESTING BLOCKS, BEDS AND METHODS” (the '387 patent).The disclosures of the '025, '068, '681 and '387 patents are herebyincorporated herein by reference.

By way of example, FIGS. 1A, 1B and 1C provide top, side and end viewsof a vehicle arresting bed constructed of cellular concrete blocks forinstallation at the end of an airport runway. As more fully described inthe '025 patent, an overrunning aircraft enters the bed via a slopedramp and encounters an array of cellular concrete blocks of increasingheight and compressive gradient strength. Such compressive gradientstrengths and the bed geometry are predetermined to enable forwardtravel to be arrested, while minimizing the potential for passengerinjury and aircraft damage. In these figures, vertical dimensions andindividual block size are expanded for clarity. An actual arresting bedmay, for example, have dimensions on the order of 150 feet in width,with a maximum height or thickness of 30 inches (or more if desired),and include thousands of blocks of four foot by four foot, four foot byeight foot or other suitable horizontal dimensions.

Arresting beds constructed pursuant to the above patents, withinstallations at major airports, have been shown to be effective insafely stopping aircraft under actual emergency overrun conditions. Forexample, the arresting of an overrunning airliner at JFK InternationalAirport by an arresting bed fabricated by the assignee of the presentinvention, was reported in the New York Times of May 13, 1999. However,in some applications, depending in part upon particular airport layout,the proximity of jet blast or other physical forces may give rise todeteriorating or destructive effects which could limit the useful lifeof an arresting bed. Material used in an arresting bed must have limitedstrength to permit compressive failure of the material withoutdestruction of the landing gear of an aircraft, for example. Thus, therequirement to limit the strength of compressible material used forarresting purposes, in turn may make the material susceptible to damageor destruction by sonic, pressure, vibrational, lift, projected graveland other characteristics and effects of jet blast from nearby aircraft,as well as from other sources, such as objects making contact with, orpeople walking on, an arresting bed at times other than during actualarresting incidents. As to jet blast phenomena in particular, measuredconditions at an end-of-runway arresting bed installation site haveincluded wind velocities to 176 MPH and 150 dB or higher sonic levels.Compressible material, such as cellular concrete, may also be subject todeteriorating effects and shortening of useful life as a result ofground water intrusion, absorption of moisture resulting from rain orsnow, thermocycling, acoustic vibrations, human traffic, otherenvironmental causes, etc.

Accordingly, objects of the present invention are to provide arrestingunits and beds, and methods relating thereto, which are new or improved,or which may have one or more of the following characteristics andcapabilities:

-   -   improved structural form without performance degradation;    -   improved resistance to some or all jet blast phenomena;    -   improved resistance to damage from pedestrian traffic;    -   improved durability in close proximity to aircraft operations;    -   improved resistance to ground water or atmospheric conditions;    -   simplified installation and replacement; and    -   improved structural integrity during shipment and installation.

SUMMARY OF THE INVENTION

In accordance with the invention, in one particular embodiment a vehiclearresting unit may include a block of compressible material (e.g.,cellular concrete), intermediate material (e.g., a foam sheet) having aresiliency characteristic, a cap assembly and a bottom tray of plasticmaterial configured to impede entry of ground surface moisture. Any suchblock may be a solid mass; alternatively, a block may comprise two ormore layers or units of material adhered or otherwise fastened orconnected together.

The cap assembly, if present, may include (i) a top tray of frangiblematerial having a top portion positioned above the intermediate materialand edge portions extending downward from the top portion and (ii) trayextensions (e.g., portions of a flexible fabric) extending from edgeportions of the top tray and adhered (via hot-melt glue or otherwise) toside surfaces of the block. The top tray, which is fabricated to readilybreak during vehicle arrestment, may be made of molded plastic materialwith upper parts of flexible fabric tray extensions molded into theplastic material. The bottom tray, if present, may include a lowersurface bordered by beveled edges configured to form water drainagechannels when two of the vehicle arresting units are positionedside-by-side on a supporting surface to provide a vehicle arresting bed.

Also in accordance with the invention, in one embodiment a method offabricating a vehicle arresting unit may include some or all of thefollowing steps, which may be employed in any suitable order:

(a) fabricating a bottom tray having a lower surface bordered by bevelededges configured to form water drainage channels when two of such bottomtrays are positioned side-by-side on a supporting surface; and

(b) forming a block of compressible material by pouring predeterminedmaterial into a mold configuration including the bottom tray, to providea vehicle arresting unit comprising the block with the bottom tray atthe bottom of the block;

(c) fabricating a cap assembly including a top tray and tray extensionsextending from edges of the top tray;

(d) positioning the top unit above the block of compressible material;and

(e) adhering the tray extensions to side surfaces of the block ofcompressible material.

The method may further include, between steps (c) and (d) or otherwise,the step of:

(x) positioning intermediate material on top of the block ofcompressible material so that the intermediate material will bepositioned between the top assembly and the top of the block, theintermediate material having a force transmission mitigationcharacteristic. In addition to such step (x) the method may include,between steps (x) and (d) or otherwise, the step of:

(y) positioning a section of sheet material (e.g., flexible fabric)below such bottom tray and adhering portions thereof to side surfaces ofthe vehicle arresting unit.

For a better understanding of the invention, together with other andfurther objects, reference is made to the accompanying drawings and thescope of the invention will be pointed out in the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are respectively a plan view, and longitudinal andtransverse cross-section views, of a vehicle arresting bed.

FIG. 2 is a three-dimensional type of view of an embodiment of a vehiclearresting unit in accordance with the invention.

FIG. 3 is a vertically-separated view of elements of the FIG. 2 vehiclearresting unit.

FIG. 4 shows the cap assembly of the vehicle arresting unit of FIGS. 2and 3.

FIG. 5 is a partial sectional view of the cap assembly of FIG. 4.

FIG. 6 shows the bottom tray of the vehicle arresting unit of FIGS. 2and 3.

FIG. 7 shows portions of two vehicle arresting units, each of the formshown in FIG. 2, placed side by side on a supporting surface.

FIG. 8 illustrates a bottom tray as in FIG. 6 positioned within anopen-bottom mold prior to introduction of block material in liquid form.

FIG. 9 is a flow chart useful in describing one method of fabricating avehicle arresting unit in accordance with the invention.

FIG. 10 is a flow chart useful in describing another method offabricating a vehicle arresting unit in accordance with the invention.

DESCRIPTION OF THE INVENTION

FIG. 2 illustrates an embodiment of a vehicle arresting unit 10 pursuantto the invention. By way of example, this arresting unit may havehorizontal dimensions of four feet by four feet and be six to thirtyinches (or more) thick. FIG. 3 provides a vertically-separated view ofelements of the FIG. 2 arresting unit. The drawings are not necessarilyto scale; some dimensions may be altered for better visual presentation.

As shown, vehicle arresting unit 10 includes a block 12 of compressible(or otherwise deformable) material having top, bottom and side surfacesand a top to bottom thickness. Block 12 may be cellular concretefabricated in accordance with the '068 patent or otherwise, or may beformed of phenolic, ceramic, foam glass or other suitable material. Asdescribed in the '025 patent, for vehicle (e.g., aircraft) arrestingapplications utilize arresting material having selected strengthcharacteristics (e.g., strength during compressive failure) suitable tomeet dual objectives of enabling aircraft travel to be arrested (i.e.,forward motion stopped) within a desired distance, while also avoidingserious passenger injury or aircraft damage such as landing gearfailure. Thus, an objective is to avoid “abrupt deceleration,” which forpresent purposes is defined as deceleration at a rate exceeding 1.4 g(where 1 g represents 32 feet per second squared). For example, cellularconcrete fabricated so as to provide a compressive gradient strengthranging between 60 to 80 psi (pounds per square inch) over a 60 to 80percent penetration range has been found suitable for use in anarresting bed for aircraft arrestment. The term “arrestment” is definedas the process of decelerating and stopping forward motion of a vehicle,such as an aircraft. Fabrication and testing of cellular concrete forsuch applications is described in the '068 and '681 patents.

As visible in FIG. 3, in this embodiment vehicle arresting unit 10includes intermediate material 14 positioned above the top surface ofblock 12. Intermediate material 14 may be a sheet or layer of foammaterial, such as closed-cell polyethylene foam, other plastic foam orother suitable material selected to provide a resiliency characteristic.To provide such characteristic, intermediate material 14 may typicallyhave one or more of pliable, compressible or resilient properties. Toreduce transmission of effects of external phenomena in the context ofthe combination of components comprising arresting unit 10, intermediatematerial 14 may be selected to provide a force transmission mitigationcharacteristic consistent with such resiliency characteristic. Suitablematerial and thickness can be specified by skilled persons in particularapplications in view of the nature and severity of applicable phenomena(e.g., in view of the level of jet blast expected and proximity to anactive runway in intended usage). For present purposes, the term“mitigation characteristic” is used consistent with the ordinarydictionary sense of “mitigate” of causing to become less harsh, hostileor severe, and may include one or more of spreading, dispensing,diluting, deflecting, dissipating, attenuating, absorbing, cushioning,or generally lessening destructive effects of noise, vibration, physicalcontact, etc. on a surface or layer below material having a forcetransmission mitigation characteristic.

In a presently preferred embodiment employing a cellular concrete block,one-quarter inch thick closed-cell polyethylene foam material isincluded for aircraft arresting bed applications. Such a foam sheet isthus considered to provide an adequate force mitigation characteristicsuitable for a typical application. In other embodiments subject todifferent levels of external phenomena (e.g., higher or lower levels ofjet blast phenomena) the intermediate material 14 may comprise adifferent type of plastic foam or other suitable material and may bethicker, thinner, include one or more layers or may be omitted. Thus, insome applications cap assembly 20 (to be described) may provide anadequate level of isolation of the block 12 from the external phenomenalevels actually present, without inclusion of intermediate material 14.As will be further described, in FIG. 2 intermediate material 14 iscovered by cap assembly 20 and is not visible.

Arresting unit 10, as illustrated, includes a cap assembly 20 positionedas the top element of the arresting unit. In this configuration, thearresting unit may be considered to be capped by the cap assembly 20. Aswill be further discussed, in installations in which an arresting bed ispositioned in relatively close proximity to operating aircraft, jetblast phenomena and other external forces may have deleterious effectson compressible materials of limited strength suitable for arresting bedapplications. Pursuant to the invention, cap assembly 20 in combinationwith other elements of arresting unit 10 provides increased protectionfrom or resistance to such effects, or both.

FIG. 4 shows cap assembly 20 separately and FIG. 5 is a sectional viewof a corner portion of cap assembly 20. Cap assembly 20 includes a toptray 22 and tray extensions 24, which may be portions of flexiblefabric, such as a synthetic fabric or other suitable material, polyesterscrim material, etc. As illustrated, top tray 22 has a flat top portionand edge portions 23 extending downward from the top portion. In apresently preferred embodiment, top tray 22 is fabricated of frangiblematerial and has a strength to readily fracture when impacted during avehicle arrestment, while being strong enough to provide to otherelements of the arresting unit at other times a level of protectionagainst environmental exposure and other external forces such asdiscussed above. Thus, in the absence of a different objective for aparticular application, a general objective is to fabricate a capassembly of components and materials such that the cap assembly has abreaking strength to readily break during vehicle arrestment withoutsubverting the selected strength characteristics of the compressiblematerial of block 12 as discussed above.

Consistent with the configuration illustrated in FIG. 5, top tray 22 maybe molded of suitable thermoset or other material, with application ofmolding techniques available to skilled persons, or otherwise suitablyfabricated. As represented in FIG. 5, in a presently preferredembodiment the tray extensions may be provided by use of flexible fabricwhich may comprise one or more central portions with the tray extensions24 extending therefrom and visible in FIGS. 4 and 5. With thisconfiguration, the central portion or portions may be introduced into asuitable molding process so that each central portion is molded into thefrangible material of the top tray 22 (for example, molded into the flattop portion, as indicated in FIG. 5 at 25, as well as into the downwardextending edge portions 23) with the tray extensions 24 extending fromthe lower edge of the edge portions 23, in the manner illustrated. Forthis embodiment the top tray may be molded of polyester plasticmaterial, for example, with flexible fabric consisting of one or moresections of any appropriate form of material, such as netting or otherappropriate type of open weave or scrim type of fabric suitable for usein a molding process as described. In other embodiments, the top traymay be formed of any suitable material as determined by skilled persons.The flexible fabric may be formed of polyester or other suitablematerial of a strength and construction configured to readily rip, tearor otherwise break during a vehicle arrestment, while being strongenough to provide a level of strength to aid in holding the elements ofarresting unit in position relative to each other, at other times. Inother embodiments tray extensions 24 may be provided in forms and shapessuitable for particular applications, may comprise other materials(e.g., sheet material such as fabric, plastic or metal, etc., solid orperforated, etc.) suitable for particular applications and may beattached to top tray 22 in any suitable manner, as may be determined byskilled persons having an understanding of the invention.

In the FIG. 2 configuration the tray extensions 24 may be glued orotherwise adhered to sides of the arresting unit, as will be furtherdescribed. In the separated view of FIG. 3, for purposes of illustrationthe tray extensions 24 are shown extending outward from the edgeportions of top tray 22 of cap assembly 20. FIG. 2 represents a finishedform of arresting unit 10 with tray extensions 24 adhered to the sidesof the arresting unit. For purposes of clarity of presentation the trayextensions 24 are represented as being transparent in FIG. 2.

In an exemplary embodiment, the top portion of top tray 22 may have athickness (e.g., as shown in cross-section in FIG. 5) of nominallyone-eighth inch and the edge portions 23 may have a thickness ofnominally one-tenth inch and a vertical dimension of at least one-halfinch. In other embodiments such dimensions may be different, asdetermined to be suitable for particular applications. For presentpurposes, the term “nominal” or “nominally” is used to identify a valueor dimension within plus or minus fifteen percent of a stated referencevalue, dimension or range. The word “frangible” is used in its ordinarydictionary sense of being breakable or shatterable without necessarilyimplying weakness or delicacy. In some implementations, a vehiclearresting unit may omit a cap assembly, intermediate material, or both,and utilize one or more of a flat top protective sheet, flexiblesheeting, a water resistant coating, some other suitable top element ornone of these, in view of the composition of the block 12, theparticular conditions of use, etc.

As illustrated, arresting unit 10 of FIGS. 2 and 3 further includes abottom tray 30 positioned as the bottom element of the vehicle arrestingunit. FIG. 6 shows bottom tray 30 separately. As shown, the bottom trayhas a bottom portion 32 (positioned below the bottom surface of block 12and therefore not visible in FIGS. 2 and 3) and edge portions 34extending upward from the bottom portion 32. With this arrangement thebottom tray is configured to impede entry of ground surface moistureinto the block 12.

Additional features of bottom tray 30, as illustrated in thisembodiment, include the following. As shown, the lower surface of bottomtray 30 is bordered (e.g., on all four sides) by beveled edges 34 a,which may be considered to comprise the lower portions of the edgeportions 34. thus, the edge portions 34 are configured to provide thebeveled edges 34 a. The beveled edges (e.g., beveled at 45° or othersuitable angle) are configured to form water drainagechannels—especially when two of the vehicle arresting units 10 areplaced side-by-side on a supporting surface. This will be describedfurther with reference to FIG. 7. As shown in FIG. 6, bottom portion 32of the bottom tray includes raised channel portions 36 which aredimensioned and shaped to enable insertion of the lifting prongs of acommon form of fork lift (e.g., fork lift truck) to facilitate liftingand placement of the arresting unit 10. In this embodiment there arealso included flat cover sections 38 arranged to extend across the loweraccess to the channels 36 which would otherwise be open across thebottom extent thereof. In this configuration, cover sections 38 may, forexample, be molded in place or formed of flat sections of suitableplastic or other material which are bonded, glued, heat welded orotherwise fastened to the bottom surface of the bottom tray 30 so as tocover upward access to the channels 36, while permitting lateral access(e.g., by fork lift prongs).

In a presently preferred embodiment, the bottom tray 30 may be molded ofplastic material (e.g. thermoplastic polystyrene material). Bottomportion 32 and edge portions 34 may have a thickness of nominallyone-tenth inch and edge portions 34 may have a height of at least oneinch upward from the bottom portion (e.g., including the height of thelower beveled portion 34 a). In other embodiments any and all dimensionsmay be altered as may be determined by skilled persons to be appropriatein view of particular conditions and objectives regarding specificapplications. In some embodiments, a vehicle arresting unit may omit abottom tray and utilize one or more of a flat bottom, flexible sheeting,a water resistant coating, some other suitable bottom element, or noneof these, in view of the composition of block 12, the particularconditions of use, etc.

As visible in FIG. 3, in the illustrated embodiment vehicle arrestingunit 10 may further include a section (e.g., one or more sections) ofsheet material having a central part positioned below bottom tray 30 andhaving upward extending parts which, in FIG. 2, are adhered to sidesurfaces of block 12. As shown in FIG. 3, sheet material section 40 hasa central part and four outward extending parts, one on each side of thecentral part. In FIG. 2, sheet material section 40 is represented asbeing transparent for purposes of clarity of presentation of thecomplete arresting unit 10. However, it will be understood that in FIG.2 the central part of section 40 has been brought up against the bottomsurface of bottom tray 30 and the extending parts of which were outwardextending in FIG. 3 have now been made to extend upward and have beenadhered (by adhesive or in any suitable manner) to the side surfaces ofblock 12. The upward extending parts of sheet material section 40 may beadhered to the sides of block 12 directly or indirectly (e.g.,positioned beneath or over the tray extensions 24 of flexible fabricwhich are discussed above). For present purposes, “adhered to sidesurfaces” and similar phrases are defined as including adhered directlyas well as indirectly (e.g., overlaying something directly adhered).With sheet material section 40 adhered to block 12 as described, theupward extending parts thereof may be provided with openings tofacilitate fork lift prong access to the transverse or laterallyextending slots formed between portions 36 and 38 (e.g., access asrepresented by arrow 37 in FIG. 6). Sheet material 40 may comprise asuitable fabric (e.g. netting, scrim, etc.) or other material such asplastic, metal, etc., perforated or unperforated, as may be determinedby skilled persons to be suitable for particular applications. In apresently preferred embodiment sheet material 40 comprises flexiblepolyester scrim fabric.

Referring now to FIG. 7, there are illustrated two vehicle arrestingunits positioned side-by-side on a supporting surface 44 (e.g., thesurface of a runway end section or extension). As shown, a right portionof an arresting unit 10 a is positioned next to a left portion of anarresting unit 10 b, each of which may be in the form of unit 10 of FIG.2. In a complete arresting bed, an example of which is shown in the planview of FIG. 1A, pursuant to the present invention each side-by-sidepositioning of two blocks may be represented by the FIG. 7configuration.

With this side-by-side arrangement, the beveled edges 34 a (borderingthe bottom surface of each arresting unit supported by surface 44) ofadjacent vehicle arresting units 10 a and 10 b positioned in abuttingarrangement, as shown, provide a water drainage channel along thesupporting surface 44. Thus, in the FIG. 7 embodiment, the two adjacentbeveled edges 34 a of respective arresting units 10 a and 10 b are shownabutting (for example, spaced about one-half inch or more apart) and, inconjunction with the supporting surface 44, form a water drainagechannel of triangular cross section and extending along the full lengthof the abutting sides of the units. In the context of a completearresting bed (e.g., of the type shown in FIG. 1A) wherein arrestingunits are arranged in columns and rows, the beveled edges of theindividual units may be arranged to provide water drainage channels on acontinuous basis extending the width or length of the arresting bed, orboth. Also, the fork lift prong channels (e.g., raised channel portion36 providing access as at 37 of FIG. 6) and spacing between arrestingunits may aid in removal of water and moisture as to each individualarresting unit, by providing access for drainage or air circulation viathe water drainage channels formed by beveled edges 34 a.

With respect to methods of fabricating vehicle arresting units, FIG. 8is a simplified side view representation of a four-sided mold or formconfiguration including left side 51, right side 52 and far side 53,with the near side removed to enable viewing of the placement of abottom tray 30 (e.g., as shown in FIG. 6) within the mold. As shown, themold has neither a top nor a bottom and both the mold and the bottomtray 30 rest upon a supporting surface 56. This mold configuration, orsuitable alternatives as may be determined by skilled persons, may beemployed in methods of fabricating vehicle arresting units, as will bedescribed.

As applicable to arresting beds installed at airports, relevant externalphenomena comprise jet blast phenomena, which may include sonic,vibrational, pressure, lift, erosive (e.g., by airborne gravel) andother characteristics and effects, as well as compressive and otherforces resulting from persons or objects making contact with anarresting bed other than during actual arresting incidents. Describedcomponents of the arresting unit 10 may be selected to reduce ormitigate effects of such external phenomena on block 12 (e.g., provide alevel of protection to block 12 relative to external phenomena incidenton cap assembly 20) and thereby provide a force transmission mitigationcharacteristic as described above, to enhance arresting unit resistanceto such phenomena. At the same time, the components and the compositearresting unit itself must not be so strong or force resistant as tosubvert the basic required parameters of energy absorption viacompressive failure of the block of compressible material with desiredcharacteristics upon contact by the wheel of an aircraft overrunning arunway. Thus, for example, the cap assembly should be readily breakableupon contact by a vehicle wheel during arrestment, so as not tosignificantly alter the selected strength characteristics available byuse of the block of compressible material, as discussed above. Arrestingunits as described thus provide intended compressive failure ofarresting units with predetermined failure characteristics whenarresting a vehicle, while providing improved resistance to deleteriouseffects of external phenomena in the period prior to occurrence of anarrestment.

FIG. 9 is a flow chart useful in describing an example of a methodutilizing the invention.

At 61, a bottom tray (e.g., bottom tray 30 of FIG. 6) is fabricated. Asdescribed, bottom tray 30 has a lower surface bordered by beveled edgesconfigured to form water drainage channels when two bottom trays arepositioned side-by-side on a supporting surface. Bottom tray 30 mayinclude upward extending edge portions and be configured to protectblock 12 from ground water and moisture absorption effects. Transverseaccess slots for access by fork lift prongs may also be provided, aspreviously described.

At 62, a block 12 of compressible material having characteristicsappropriate for a vehicle arresting application is provided. As noted,the block may comprise cellular concrete having an appropriatecompressive gradient strength as described in the '068 patent or othersuitable material, such as phenolic, ceramic, foam glass, etc. Foraircraft arresting bed applications the block may typically havedimensions of approximately four feet by four feet by six to 30 inchesin thickness. In this embodiment block 12 may be formed by pouringsuitable material into a mold configuration (e.g., as described withreference to FIG. 8) including the bottom tray 30, to provide block 12with tray 30 below the bottom surface of the block. In this arrangement,in addition to conforming to the bottom surface of the block, the upwardextending edge portions of tray 30 provide additional protection againstdamage and moisture exposure to the lower part of block 12.

At 63, a section of sheet material (e.g., flexible fabric section 40 ofFIG. 3) is positioned below bottom tray 30. In this embodiment, parts ofthe sheet material section 40 which extend out from under bottom tray 30are then brought upward and adhered to side surfaces of the block 12 andthereby side surfaces of the arresting unit 10. In this regard, it willbe appreciated that the upward extending parts of sheet material section40 may be adhered directly to the sides of block 12 or indirectly byadherence over previously adhered tray extensions 24 extending downwardfrom top tray 22, depending upon whether the respective upper or lowerfabric portions are adhered first, as may be determined by skilledpersons in particular implementations of the invention. To provideadherence of the upward extending parts of the sheet material section40, suitable adhesives or other materials, as may be determined asappropriate in particular implementations, may be employed. When theoutward extending parts of the sheet material section 40 are broughtupward they may cover the access openings (e.g., 37 in FIG. 6) for forklift prongs, unless suitable openings in the sheet material havepreviously been provided. Alternatively, suitable openings through thesheet material parts can be provided after they are brought intoposition and thereby cover the access openings 37. For clarity ofpresentation, sheet material section 40 may be depicted as beingtransparent in certain views (e.g., FIG. 2). However, a variety of formsand type of fabric may be employed, as determined to be appropriate byskilled persons. In some implementations it may be determined to beappropriate to omit the bottom fabric section and place reliance onother components of the arresting unit as adequate to maintain arrestingunit integrity. With inclusion of bottom fabric section 40, increasedpositional stability and adherability of an arresting unit to asupporting surface may be provided.

At 64, intermediate material 14 is positioned above the top surface ofblock 12. Intermediate material 14 may comprise a layer of closed-cellor other foam or other material providing a desired force transmissionmitigation characteristic with respect to external phenomena. Suchmaterial may or may not have energy absorption properties, dependingupon the particular material selected and may have a thickness up toone-half inch or more. In a currently preferred embodiment intermediatematerial 14 is provided in the form of a sheet of polyethylene foam ofapproximately one-quarter inch thickness. In some embodimentsintermediate material 16 may be omitted (e.g., in view of a low expectedseverity of external phenomena).

At 65, a cap assembly (e.g., cap assembly 20 of FIG. 4) is fabricated.As described, cap assembly 20 may include a top tray 22 molded ofthermoplastic material and tray extensions 24 of flexible fabric orother material extending from edges to the top tray. As described withreference to FIG. 5, in one embodiment top tray 22 may have upperportions of tray extensions comprising flexible fabric molded into theplastic material during molding, as represented at 25. In a currentlypreferred embodiment, top tray 22 is formed of a plastic material havingproperties to enable it to readily break (e.g., fracture) during anaircraft arrestment. This enables cap assembly 20 to initially protectblock 12 from incidental damage, but to break upon contact by anaircraft wheel during an arrestment without being strong enough tomaterially alter the overall energy absorption characteristics providedduring compressive failure of block 12.

At 66, a cap assembly (e.g., cap assembly 20 as previously fabricated)is positioned above the intermediate material (e.g., intermediatematerial 14 in this embodiment) which has been positioned above the topsurface of block 12. As represented in FIG. 2, with cap assembly 20 inposition at the top of arresting unit 10, the edge portions of the capassembly may extend downward far enough to cover the intermediatematerial 14 (e.g., as shown in FIG. 3) so that the edges of theintermediate material are not visible in the completed arresting unitshown in FIG. 2.

At 67, the tray extensions (e.g., portions 24 visible in FIG. 3) areadhered to side surfaces of the block 12 and thereby side surfaces ofthe arresting unit 10. As described with reference to the bottom sectionof sheet material 40, adherence may be directly to sides of block 12 orindirectly via adherence overlaying the parts of the sheet material 40,depending on the order of adherence as determined in specificembodiments. To provide adherence of the tray extensions 24 suitableadhesives or other materials may be used as determined as appropriate inparticular implementations. With side adherence of the tray extensions24 (shown transparent in FIG. 2) in a presently preferred embodiment ithas been determined that positioning of cap assembly 20 and integrity ofthe complete arresting unit 10 is adequately maintained under typicalconditions after installation of arresting units to form an arrestingbed. In specific implementations additional or different arrangementsmay be provide by skilled persons for integrity of installation or otherpurposes.

FIG. 10 is a flow chart useful in describing another example of a methodutilizing the invention.

At 61A, a cap assembly (e.g., cap assembly 20 of FIG. 4) is fabricated.As described, cap assembly 20 may include a top tray 22 molded ofthermoplastic material and tray extensions 24 of flexible fabric orother material extending from edges to the top tray. As described withreference to FIG. 5, in one embodiment top tray 22 may have upperportions of tray extensions comprising flexible fabric molded into theplastic material during molding, as represented at 25. In a currentlypreferred embodiment, top tray 22 is formed of a frangible plasticmaterial (including glass fibers) having properties to enable it toreadily break (e.g., fracture) during an aircraft arrestment. Thisenables cap assembly 20 to initially protect block 12 from incidentaldamage, but to break upon contact by an aircraft wheel during anarrestment without being strong enough to materially alter the overallenergy absorption characteristics provided during compressive failure ofblock 12.

At 62A, a bottom tray (e.g., bottom tray 30 of FIG. 6) is fabricated. Asdescribed, bottom tray 30 may include upward extending edge portionswith beveled lower edges and be configured to protect block 12 fromground water and moisture absorption effects. Transverse access slotsfor access by fork lift prongs may also be provided, as previouslydescribed.

At 63A, a block 12 of compressible material having characteristicsappropriate for a vehicle arresting application is provided. As noted,the block may comprise cellular concrete having an appropriatecompressive gradient strength as described in the '068 patent or othersuitable material, such as phenolic, ceramic, foam glass, etc. Foraircraft arresting bed applications the block may typically havedimensions of approximately four feet by four feet by five to 30 inches(or more) in thickness. In this embodiment block 12 may be formed bypouring suitable material into a mold configuration (e.g. as describedwith reference to FIG. 8) including the bottom tray 30, to provide block12 with tray 30 below the bottom surface of the block. In thisarrangement, in addition to conforming to the bottom surface of theblock, the upward extending edge portions of tray 30 provide additionalprotection against damage and moisture exposure to the lower part ofblock 12.

At 64A, a section of sheet material (e.g., flexible fabric section 40 ofFIG. 3) is positioned below bottom tray 30. In this embodiment, parts ofthe sheet material section 40 which extend out from under bottom tray 30are then brought upward and adhered to side surfaces of the block 12 andthereby side surfaces of the arresting unit 10. In this regard, it willbe appreciated that the upward extending parts of sheet material section40 may be adhered directly to the sides of block 12 or indirectly byadherence over previously adhered tray extensions 24 extending downwardfrom top tray 22, depending upon whether the respective upper or lowerfabric portions are adhered first, as may be determined by skilledpersons in particular implementations of the invention. To provideadherence of the upward extending parts of the sheet material section40, suitable adhesives or other materials, as may be determined asappropriate in particular implementations, may be employed. When theoutward extending parts of the sheet material section 40 are broughtupward they may cover the access openings (e.g., 37 in FIG. 6) for forklift prongs, unless suitable openings in the sheet material havepreviously been provided. Alternatively, suitable openings through thesheet material parts can be provided after they are brought intoposition and thereby cover access openings 37. For clarity ofpresentation, sheet material section 40 may be depicted as beingtransparent in certain views (e.g., FIG. 2). However, a variety of formsand types of fabric may be employed, as determined to be appropriate byskilled persons. In some implementations it may be determined to beappropriate to omit the bottom fabric section and place reliance onother components of the arresting unit as adequate to maintain arrestingunit integrity. With inclusion of bottom fabric section 40, increasedpositional stability and adherability of an arresting unit to asupporting surface may be provided.

At 65A, intermediate material 14 is positioned above the top surface ofblock 12. Intermediate material 14 may comprise a layer of closed-cellor other foam or other material providing a desired force transmissionmitigation characteristic with respect to external phenomena. Suchmaterial may or may not have energy absorption properties, dependingupon the particular material selected and may have a thickness up toone-half inch or more. In a currently preferred embodiment intermediatematerial 14 is provided in the form of a sheet of polyethylene foam ofapproximately one-quarter inch thickness. In some embodimentsintermediate material 16 may be omitted (e.g., in view of a low expectedseverity of external phenomena).

At 66A, a cap assembly (e.g., cap assembly 20 as previously fabricated)is positioned above the intermediate material (e.g., intermediatematerial 14 in this embodiment) which has been positioned above the topsurface of block 12. As represented in FIG. 2, with cap assembly 20 inposition at the top of arresting unit 10, the edge portions of the capassembly may extend downward far enough to cover the intermediatematerial 14 (e.g., as shown in FIG. 3) so that the edges of theintermediate material are not visible in the completed arresting unitshown in FIG. 2.

At 67A, the tray extensions (e.g., portions 24 visible in FIG. 3) areadhered to side surfaces of the block 12 and thereby side surfaces ofthe arresting unit 10. As described with reference to the bottom sectionof sheet material 40, adherence may be directly to sides of block 12 orindirectly via adherence overlaying the parts of the sheet material 40,depending on the order of adherence as determined in specificembodiments. To provide adherence of the tray extensions 24 suitableadhesives or other materials may be used as determined as appropriate inparticular implementations. With side adherence of the tray extensions24 (shown transparent in FIG. 2) in a presently preferred embodiment ithas been determined that positioning of cap assembly 20 and integrity ofthe complete arresting unit 10 is adequately maintained under typicalconditions after installation of arresting units to form an arrestingbed. In specific implementations additional or different arrangementsmay be provided by skilled persons for integrity of installation orother purposes.

If desired, a sealant may be applied to the arresting unit 10 (e.g., toside surfaces as selected) to provide a water resistant characteristic.For example, polyurethane or epoxy coatings, or both, may be determinedto be appropriate for this purpose, however other suitable materials maybe employed and may provide both water resistance and some degree ofadditional resistance to external phenomena, such as ultravioletradiation.

With an understanding of the invention, it will be apparent to skilledpersons that steps of methods pursuant to the invention may be modified,varied as to order, omitted or supplemented by additional or differentsteps, or combinations of the foregoing. Also, in particularimplementations of arresting units one or more of the describedcomponents may be omitted (e.g., cap assembly, intermediate material,bottom fabric section, etc.) changed or supplemented as may bedetermined to be appropriate by skilled persons, consistent with theinvention. Skilled persons will be enabled to select suitable materials,methods and configurations as appropriate for particular applicationsand operating conditions. For example, it may be desirable to furtherglue or adhere together other components of the arresting unit.

While there have been described the currently preferred embodiments ofthe invention, those skilled in the art will recognize that other andfurther modifications may be made without departing from the inventionand it is intended to claim all modifications and variations as fallwithin the scope of the invention.

1. A vehicle arresting unit, usable for arrestment of a vehicle,comprising: a block of compressible material having top, bottom and sidesurfaces; intermediate material, having a resiliency characteristic,positioned above said top surface; a cap assembly including (i) a toptray of frangible material having a top portion positioned above saidintermediate material and edge portions extending downward from the topportion and (ii) tray extensions extending from edge portions of saidtop tray and adhered to side surfaces of said block, the top trayfabricated to readily break during arrestment of said vehicle; and abottom tray of water impervious material having a bottom portionpositioned below the bottom surface of said block and edge portionsextending upward from the bottom portion, the bottom tray configured toimpede entry of ground surface moisture.
 2. A vehicle arresting unit asin claim 1 in which said bottom tray includes a lower surface borderedby beveled edges, said beveled edges forming water drainage channelswhen two of said vehicle arresting units are positioned side-by-side ona supporting surface.
 3. A vehicle arresting bed, comprising: aplurality of vehicle arresting units, each in accordance with claim 2,arranged on a supporting surface with said beveled edges of adjacentvehicle arresting units abutting to provide water drainage channelsalong the supporting surface.
 4. A vehicle arresting unit as in claim 1,wherein said tray extensions comprise sections of flexible fabric, upperparts of which are molded into the frangible material of said top tray.5. A vehicle arresting unit as in claim 1, wherein the top traycomprises molded plastic material fabricated to readily fracture whencontacted by a tire during arrestment of said vehicle.
 6. A vehiclearresting unit as in claim 1, further comprising: a section of sheetmaterial having a central part below said bottom tray and upwardextending parts adhered to side surfaces of said block.
 7. A vehiclearresting unit, usable for arrestment of a vehicle, comprisingcompressible material having top, bottom and side surfaces, saidcompressible material configured to decelerate said vehicle duringarrestment; and a cap assembly including (i) a top tray having a topportion positioned above the top of said compressible material and (ii)tray extensions extending from said top tray and adhered to said sidesurfaces of said compressible material, the top tray fabricated toreadily fracture during vehicle arrestment.
 8. A vehicle arresting unitas in claim 7, further comprising: intermediate material positionedbetween said top surface and said cap assembly and having a resiliencyproperty.
 9. A vehicle arresting unit as in claim 7, wherein said trayextensions comprise sections of sheet material joined to the top tray.10. A vehicle arresting unit as in claim 7, wherein said tray extensionscomprise sections of flexible fabric, upper parts of which are embeddedin the top tray.
 11. A vehicle arresting unit as in claim 7, whereinsaid tray extensions comprise sections of flexible fabric, upper partsof which are molded into the top tray.
 12. A vehicle arresting unit asin claim 7, wherein the top tray comprises molded plastic materialfabricated to readily fracture when contacted by a tire during vehiclearrestment.
 13. A vehicle arresting unit as in claim 7, furthercomprising: a bottom tray having a bottom portion positioned below thebottom surface of said compressible material and side portions extendingupward from the bottom portion, the bottom tray configured to impedeentry of ground surface moisture.
 14. A vehicle arresting unit as inclaim 7, wherein said compressible material comprises a block ofcellular concrete which is compressible by a tire of said vehicle todecelerate the vehicle during arrestment, which abrupt deceleration. 15.A vehicle arresting unit as in claim 7, further comprising: a section ofsheet material having a central part below said bottom tray and upwardextending parts adhered to side surface of said compressible material.16. A vehicle arresting unit, usable for arrestment of a vehicle,comprising a cap assembly including: a top tray including a top portionand edge portions extending downward from the top portion; and trayextensions comprising sheet material portions joined to the top tray andextending downward from edges of the top tray.
 17. A vehicle arrestingunit as in claim 16, wherein said top tray comprises plastic materialand said tray extensions are flexible fabric portions joined to the toptray by having upper parts of the flexible fabric portions at leastpartially embedded in said plastic material.
 18. A vehicle arrestingunit as in claim 16, wherein said top tray comprises molded plasticmaterial and said tray extensions comprise flexible fabric portions,upper parts of which are molded into said plastic material.
 19. Avehicle arresting unit as in claim 16, wherein said top tray comprisesplastic material fabricated to fracture during arrestment of saidvehicle.
 20. A vehicle arresting unit as in claim 16, wherein said trayextensions comprise sections of polyester scrim material.
 21. A methodof fabricating a vehicle arresting unit usable for arrestment of avehicle, comprising: (a) fabricating a cap assembly including a top trayand tray extensions extending from edges of the top tray; (b) providinga block of compressible material having top, bottom and side surfaces,said block compressible to decelerate said vehicle during arrestment;(c) positioning intermediate material above said top surface, saidintermediate material having a force transmission mitigationcharacteristic; (d) positioning said cap assembly above saidintermediate material; and (e) adhering said tray extensions to sidesurfaces of the vehicle arresting unit.
 22. A method as in claim 21further comprising, between actions (a) and (b): (x) fabricating abottom tray having a bottom portion and edge portions extending upwardfrom the bottom portion; and wherein action (b) includes forming saidblock by pouring material into a mold configuration including saidbottom tray, to provide said block with said bottom tray below saidbottom surface of the block.
 23. A method as in claim 22 furthercomprising, between actions (a) and (b): (y) positioning a section ofsheet material below said bottom tray and adhering portions of thatsection of sheet material to side surfaces of the vehicle arrestingunit.
 24. A method as in claim 23, wherein action (y) comprisespositioning a section of flexible fabric.
 25. A method of forming avehicle arresting bed, comprising: fabricating a plurality of vehiclearresting units, each in accordance with actions (a) through (e) ofclaim 21; and positioning said units to cover an area of width andlength suitable to arrest travel of a vehicle entering the bed.
 26. Amethod of fabricating a vehicle arresting unit usable for arrestment ofa vehicle, comprising: (a) fabricating a bottom tray having a bottomportion and edge portions extending upward from the bottom portion; (b)forming a block of compressible material by pouring predeterminedmaterial into a mold configuration including said bottom tray, toprovide a block having the bottom tray at the bottom; (c) fabricating acap assembly including a top tray and tray extensions extending fromedges of the top tray; (d) positioning said cap assembly above saidblock; and (e) adhering said tray extensions to side surfaces of thevehicle arresting unit.
 27. A method as in claim 26, wherein action (c)comprises fabricating a cap assembly including a top tray and trayextensions comprising sections of flexible fabric.
 28. A method as inclaim 26 further comprising: (f) positioning a section of sheet materialbelow said bottom tray and adhering portions of that section of sheetmaterial to side surfaces of the vehicle arresting unit.
 29. A method offorming a vehicle arresting bed comprising: fabricating a plurality ofvehicle arresting units, each in accordance with actions (a) through (e)of claim 26; and positioning said units to cover an area of width andlength suitable to arrest travel of a vehicle entering the bed.
 30. Avehicle arresting unit, usable for arrestment of a vehicle, comprising:compressible material having top, bottom, and side surfaces, saidcompressible material configured to decelerate said vehicle duringarrestment; and a bottom tray having a bottom portion positioned belowthe bottom surface of said compressible material and including a bottomsurface bordered by at least one beveled edge, said beveled edge formingat least one water drainage channel.
 31. A vehicle arresting bedcomprising a plurality of vehicle arresting units, each in accordancewith claim 30, arranged on a supporting surface with said beveled edgesof adjacent vehicle arresting units abutting to provide at least onewater drainage channel.
 32. A vehicle arresting unit as in claim 30,wherein said bottom tray is shaped to provide transverse channelssuitable to accept fork lift prongs.
 33. A vehicle arresting unit as inclaim 30, wherein said compressible material comprises a block ofcellular concrete which is compressible by a tire of an aircraftoverrunning an end of a runway to decelerate the aircraft duringarrestment without abrupt deceleration.
 34. A vehicle arresting unit asin claim 30, further comprising a section of sheet material having acentral part below said bottom tray and upward extending parts adheredto side surfaces of said compressible material.
 35. A vehicle arrestingbed, comprising: a plurality of vehicle arresting units, each with abottom portion having a bottom surface bordered by beveled edges; thevehicle arresting units arranged on a supporting surface with saidbeveled edges of adjacent vehicle arresting units abutting to providewater drainage channels along the supporting surface.
 36. A vehiclearresting bed as in claim 35, wherein each said vehicle arresting unitcomprises: a block of compressible material having a bottom surface; anda bottom tray of plastic material having a bottom portion positionedbelow the bottom surface of said block, said bottom portion of saidbottom tray having a lower surface bordered by said beveled edges.
 37. Avehicle arresting bed as in claim 35, wherein said bottom tray includesedge portions extending upward from said bottom portion, said edgeportions configured to provide said beveled edges.
 38. A vehiclearresting unit as in claim 35, wherein said bottom tray is shaped toprovide transverse channels suitable to accept fork lift prongs.
 39. Amethod of fabricating a vehicle arresting unit usable for vehiclearrestment, comprising: (a) fabricating a bottom tray having a lowersurface bordered by beveled edges configured to form water drainingchannels when two of said bottom trays are positioned side-by-side on asupporting surface; and (b) forming a block of compressible material bypouring predetermined material into a mold configuration including saidbottom tray, to provide a vehicle arresting unit comprising said blockwith said bottom tray at the bottom of said block.
 40. A method as inclaim 39, further comprising: forming a vehicle arresting bed from aplurality of vehicle arresting units fabricated pursuant to actions (a)and (b), by positioning said units on a supporting surface with saidbeveled edges of adjacent vehicle arresting units abutting to providewater draining channels along the supporting surface.
 41. A method as inclaim 39, further comprising: (c) fabricating a cap assembly including atop tray and tray extensions extending from edges of the top tray; (d)positioning said top unit above said block of compressible material; and(e) adhering said tray extensions to side surfaces of said block ofcompressible material.
 42. A method as in claim 41, further comprising,between actions (c) and (d): (x) positioning intermediate material ontop of said block of compressible material so that the intermediatematerial will be positioned between the top assembly and the top of theblock, said intermediate material having a force transmission mitigationcharacteristic.
 43. A method as in claim 39, wherein action (a)comprises fabricating a bottom tray shaped to provide transversechannels suitable to accept fork lift prongs.
 44. A method as in claim39, further comprising positioning a section of sheet material belowsaid bottom tray and adhering portions of that section of sheet materialto side surfaces of the vehicle arresting unit.
 45. A vehicle arrestingunit as in claim 16, wherein said tray extensions comprise sections offiberglass scrim material.
 46. A vehicle arresting unit as in claim 1,wherein the tray extensions are adhered to said side surfaces of saidblock using hot-melt glue.